Paper feed roller structure for image reading apparatus

ABSTRACT

A paper feed roller (5) is divided into a first roller (5a) and a second roller (5b); a slit (58) through which about 10 to 20 sheets of documents can pass is formed between the first roller and a gate plate (57) opposite to this; and the paper fed out therefrom is fed out to a space between the second roller (5b) and a separation pad (7) in contact with this. 
     Also, there is adopted a construction in which the pressing force of a paper conveyance spring is transformed by a slide cam sliding in a direction parallel to the paper feed roller; and the paper width detection sensor is assembled by a fitting construction.

TECHNICAL FIELD

The present invention relates to an image reading apparatus such as afacsimile or image scanner and is further directed to the improvement ofthe components of such an image reading apparatus.

BACKGROUND ART

A brief explanation will be made first, referring to FIG. 41, of thegeneral configuration of an image reading apparatus (including both theone-side and two-side reading types) in which media having informationto be read (below, referred to as documents or paper) are stacked on ahopper and are sequentially taken out from the lowermost document(bottom take-out type) and the information of the document is opticallyread (two-side reading type).

In the figure, the documents 1 stacked on a document hopper 3 aresequentially taken out from the lowermost document by the coaction of apaper feed roller 5 and a document separation pad elastically pressedagainst the same. Thereafter, the documents 1 are sent to a paper ejectroller 13 via feed rollers 9 and 11 while being guided by paper guides(document stands) 17 and 19 and are ejected from there to the outsideand stacked on a stacker 15. During this feeding operation, theinformation of the document is read by a first optical reading unit 21Aand a second optical reading unit 21B. In the illustrated conventionalexample, the first optical reading unit 21A is arranged beneath adocument passage 23 and reads the information (image) on a lower surfaceof the document, while the second optical reading unit 21B is arrangedabove the document passage 23 and reads the information (image) on theupper surface of the document. Note that, the first optical reading unit21A and second optical reading unit 21B are constituted by light sourcelamps 25a and 25b; first and second reflection mirrors 27a, 29a and 27b,29b; imaging lenses 31a and 31b; and one-directional image sensors 33aand 33b.

FIG. 42 shows the general configuration of a single reading unit typeimage reading apparatus which reads both surfaces of the document byinverting the same.

In the figure, parts corresponding to those in FIG. 41 are given thesame numerals, and an explanation thereof will be omitted. Note that, inFIG. 42, the document 1 is shown supplied from the left side of thefigure reverse to FIG. 41. The document 1 is sent in the right directionin the figure by a feed belt 41, and initially the image of the lowersurface is read by the single reading unit 21. Note that, the readingunit 21 is moveable along the document stand 17, which performs asub-scanning (in a direction orthogonal to a beam scanning direction,that is, the scanning of the document feeding direction). Thissub-scanning is exactly the same in the case of FIG. 41 as well.

The document whose lower surface has been read is drawn in a direction Aof the figure (left direction) by the feed belt 41. Before the rear edgeis separated from reversing rollers 43, the feed belt 41 is reversed topass the document between the reversing rollers 43, draw it in adirection B, and drop it on the reversing stand 45. Thereafter, thereversing rollers 43 are reversed and the document 1 is supplied ontothe document stand 17 by coaction with the feed belt 41. At this time,the front and back of the document 1 are inverted from those at thefirst reading, and accordingly the image of the other surface (initialupper surface) can be read. After the completion of the readingoperation, the feed belt 41 is reversed again, and the document 1 is fedrightward in the figure and stacked on the stacker 15. Note that, atthis time, the passage switching lever 47 is opened to a position 47'.Although not particularly illustrated, if necessary, the passageswitching lever is appropriately provided also at the portion of thereversing rollers 43.

There has been a rapid reduction of size and lowering of price of themain body of data processing apparatuses. Along with this, the reductionof size and lowering of price of the peripherals have been demanded. Theimage reading apparatuses are no exceptions. There was a problem in thatwith the conventional construction of image reading apparatuses, it wasnot possible to sufficiently respond to such demands for reduction ofsize and lowering of price, that is, the greater density of themechanical components constituting the image reading apparatus andgreater ease of fabrication and assembly of the same.

A bottom take-out type automatic paper feeding apparatus is provided, asshown in FIG. 43, with a paper feed roller 5 which comes into contactwith the lower surface of a front edge portion of the document 1 stackedon the hopper 3 on the paper feeding side of the hopper 3. Theconventional bottom take-out type automatic paper feeding apparatus isconstructed so that this paper feed roller 5 is constituted by oneroller and so that the front edge of the separation pad 7B, which isprovided with flexibility, comes into surface-contact with thecircumferential surface of the paper feed roller 5, so that theseparated lowermost paper 1 is changed in its orientation slightlydownward and fed out from a space between the paper feed roller 5 andthe separation pad 7B.

The document fed out in this way is further fed while being held betweena drive roller 9a and a driven roller 9b of the feed rollers 9. When itpasses the reading portion a, an image of the image information on thepaper is formed on a light receiving cells of the CCD's 33a and 33b bylenses 31a (31b) and read. The document is then ejected to the stacker15 (FIG. 41) on the left side in that figure while being held between adrive roller 13a and a driven roller 13b of the eject rollers 13. In theconventional image reading apparatus provided with this type ofconstruction, the feed rollers 9 and 11 (FIG. 41) and eject rollers 13are synchronously driven by a feed motor 51, and the feed roller 5 isdriven to rotate in the same direction (the same direction in a sensethat when the feed roller 9 rotates in a direction supplying the paper,the paper feed roller 5 rotates in the direction supplying the paper aswell. The reverse is referred to as the "reverse direction". The same istrue also below) as the feed rollers 9 via two transmission gears 53 and55. The apparatus further is constructed so that, by raising theperipheral speed of the feed rollers 9 to be slightly higher than theperipheral speed of the paper feed roller 5, the feeding speed of thepaper after the paper is grasped by the feed rollers 9 is defined by thefeed rollers 9. At this time, there is no looseness of the paper or thelike between the feed rollers 9 and the paper feed roller 5.

The reason why the bottom take-out type automatic paper feed apparatusis used as an image reading apparatus is that the apparatus isconstituted so as to read the lower surface of the document. In theconventional bottom take-out type automatic paper feed apparatus asshown in FIG. 43, however, if the amount of the paper which is stackedis increased or the paper is thick paper, there was a problem thaterrors such as double feed, paper misfeeding, or the like were liable tooccur, so the paper feeding performance was unstable in comparison withthe top take-out type automatic paper feeding apparatus. Namely, if theamount of the stacked papers is increased, due to the weight of thepaper, the frictional force between the paper and the paper feed roller5 and between the sheets of paper is increased, so that double feedingbecomes easy, while if the paper is a thick paper, the passingresistance when the paper passes between the paper feed roller 5 andseparation pad 7B becomes large, so that paper misfeeding easily occurs.Also, in the conventional apparatus of this type of construction, tostabilize the feeding of the paper, it was necessary to set the paper onthe document stand in an inclined state so that the front edge of thepaper at the lower end projects out in the paper feeding direction to agreater extent at the setting of the paper, and there arose a problemthat the work load of the operator became greater.

Further, in the conventional apparatus, the paper feed roller and feedrollers are rotated in the same direction, and the paper is separated bythe difference in the peripheral speed between the paper feed roller 5and feed rollers 9, therefore a skew at the time of the setting of thepaper (skew feeding of the paper) appeared on the reading image as itwas. When the paper feed roller was rotated fast so as to improve thethrough-put, double feed was apt to occur, and therefore there aroseanother problem in that the improvement of the through-put wasrestricted.

For example, in the bottom take-out type automatic paper feeding unitmentioned above, to cope with documents having a wide range of paperquality, it was necessary to push the documents against the paper feedroller 5 and make the biasing force of the conveyance spring 7A forseparating the paper variable. In the conventional apparatus, a variablemechanism of this conveyance spring having a construction as shown inFIGS. 44 and 45 has been used. Namely, there has been adopted aconstruction in which a fixed spring 7a and a moveable spring 7b areprovided as the conveyance spring, the moveable spring 7b is providedaround a pivot shaft 61 in parallel to the paper feed roller 5 so thatit can swing and is biased by a biasing projection 63 in a direction tomove it away from the paper feed roller 5. On the other hand, arectangular cam 67 which is pivotally provided on a seat plate 65 of thefixed spring 7a in an eccentric position is made to abut against anengagement piece 69 formed by bending the moveable spring 7b. Therectangular cam 67 is pivoted by the lever 71, whereby the engagementpiece 69 is pushed by the rectangular cam 67 in a counterclockwisedirection in FIG. 44, to elastically press the moveable spring 7bagainst the paper feed roller 5.

According to this conventional construction, the moveable spring 7b ismade to abut against the paper feed roller 5 and is separated therefromby the operation of the lever 71, whereby it is possible to change thepaper separation ability of the automatic paper feeding apparatus, butthe lever 71 is projected from the rectangular cam 67, and thereforethere arisen a problem in that the apparatus can not be constituted incompact size, and the number of parts is large, and thus the apparatusconstruction has become complex.

Also, in an image reading apparatus, a paper width detection sensor fordetecting the width dimension of the fed paper is provided, but thereflectance of the surface greatly changes for each document, andtherefore it is difficult to directly detect the document by an opticalsensor. Thus, a sensor provided with a lever which physically comes intocontact with the paper and swings is provided inside the paper passage.This type of conventional sensor is constructed, as shown in FIG. 46, sothat a sensor bracket 81 is fixed on a paper feed frame by a screw 83,and a sensor arm 91 provided with a shielding plate 87 and a detectionlever 89 on its two ends is pivotally fixed on a collar 85 secured tothis sensor bracket by the screw. When the paper strikes the detectionlever 89 from a direction indicated by an arrow X in the figure, thesensor arm 91 swings in the counterclockwise direction in the figure andthe shielding plate 87 retracts from the light path of an opto-electricsensor 93 (the shielding plate 87 is usually positioned inside the lightpath of the opto-electric sensor 93 and cuts the beam), to detect thepaper. Such a construction, however, had the drawback that the assemblyof the sensor was cumbersome.

Also, the light source lamps 25 (25a, 25b) of the reading units 21 (21A,21B) (FIG. 41) must be replaced when amount of the light is lowered, butthe conventional attachment structure for enabling that replacement wasone in which, for example as shown in FIG. 47, a lamp unit 97constituted by the light source lamp 25 and its lamp frame 95 wasinserted or detached into or from the side of the apparatus in alongitudinal direction of the lamp to attach or detach the same. Here,in FIG. 47, 92 is a socket which is fixed on the lamp frame 95 andsupports the two ends of the lamp 25, and 99 is a plate spring attachedto the main body. This plate spring 99 has a function of elasticallypressing the inserted lamp frame 95 to affix the same. Reference numeral17 is a transparent document stand, and 27a is a first reflectionmirror. In the case of such a construction, however, it is necessary toprovide an opening for performing the attachment and detachment of thelamp unit 97 to the side of the reading unit and the side of theapparatus frame, and it is necessary to reinforce the frame to make upfor the strength lost by this opening, and therefore there is a problemin that the frame construction becomes complex. Since the lamp unit 97was moved in the longitudinal direction, there existed a problem in thespace required for the replacement work and the workability.

An object of the present invention is to solve the problems as describedabove. The invention has as its gist to make improvements in a bottomtake-out type automatic paper feeding apparatus so as to more correctlyperform the separation and supply of the paper, to increase the amountof the paper able to be stacked on the document stand, to smoothlyperform also the supply of thick paper documents, and to enable thecorrection of the skew.

Further, so as to solve the above-mentioned problems, the presentinvention has as its gist to obtain a technical means with which thepaper feeding portion and reading portion can be constituted in acompact size, the fabrication and assembly of the constituent materialsare easy, and accordingly a document reading apparatus greatly reducedin size in comparison with the conventional apparatus is provided at alower cost.

DISCLOSURE OF THE INVENTION

According to the first aspect of the invention, there is adopted aconstruction in which the paper feed roller unit, which isconventionally comprised of one roller, is divided into a first rollerand a second roller. The first roller is arranged at the front edgeportion of the hopper so as to come into contact with the lower surfaceof the front edge portion of the stacked documents 1, and the secondroller is arranged on the paper feeding side of the first roller. Aseparation pad which conducts the separation of the papers inassociation with the paper feed rollers is brought into contact with thesecond roller. On the other hand, the front edge of the gate plate ismade to face the circumferential surface of the first roller. A slitthrough which about 10 to 20 sheets of paper can pass is formed betweenthis front edge and the first roller. The paper fed out from this slitis fed to the contact portion between the second roller and theseparation pad. The gate plate is arranged in a state of inclinationwith respect to the normal of the first roller so that its lower endside is inclined in the paper supplying direction.

The first roller and the second roller are driven in the same directionat an equal peripheral speed. When an automatic paper feeding apparatushaving the above-described construction is provided in an image readingapparatus having feed rollers, the feed rollers and paper feed rollersare connected via one transmission gear and a one-directional clutch.When the feed rollers are reversed (rotated in the paper returndirection), the paper feed rollers rotates forward (rotate in the paperfeed-out direction). At the same time, when the feed rollers are rotatedforward, the paper feed rollers are placed in a free rotation state bythe release of connection of the aforesaid one-directional clutch.

The inclination angle of the aforesaid gate plate facing the firstroller is preferably set to a large angle when the paper is a thickpaper, while is set to a small angle when the paper is a thin paper.Accordingly, as a construction that can pivot around a support shaftparallel to the shaft of the first roller and can be affixed in place aswell, it is effective if the gate plate can be changed in itsinclination angle in accordance with the thickness or amount of thepapers to be stacked.

To automatically perform the adjustment of the inclination angle of thegate plate in accordance with the thickness or amount of the paper, itis possible to adopt a construction in which a motor which can rotate inthe forward and reverse directions and drive the gate plate to rotatearound the support shaft is controlled by the detection signals of anempty sensor detecting the presence or absence of paper on the hopperand a first paper feed detection sensor detecting the paper between thefirst roller and the second roller. Namely, control is performed sothat, when the empty switch detects the nonexistence of paper, the gateplate is restored to the set minimum inclination angle; when the firstroller rotates forward in a state where the document 1 is stacked on thehopper, the feed out of the paper from the slit is monitored by thefirst paper feed detection sensor; if the first paper feed detectionsensor does not detect paper even though a predetermined time haselapsed, a rotation instruction is given to the gate opening and closingmotor so as to pivot the gate plate in a direction for inclination ofthe gate plate by exactly a predetermined angle; and when the firstpaper feed detection sensor still does not detect paper even though ithas been on standby in this state for a predetermined time, a rotationinstruction for further inclining the gate plate by exactly apredetermined angle is given to the gate opening and closing motor. Thisis repeatedly performed. When the first paper feed detection sensordetects the paper, control is performed so that the gate plate isretained at the angle at that time.

In an automatic paper feeding apparatus having the above-describedconstruction, 10 to 20 sheets of paper are primarily separated and fedout from the slit by the first roller and the gate plate. The lowermostend sheet of paper is separated and fed out from these primarilyseparated papers by the second roller and separation pad. The amount ofthe paper to be primarily separated is substantially constantirrespective of whether the amount of paper on the document stand 2 islarge or small, and accordingly the operation of separation of the paperby the second roller and the separation pad is carried out under almostthe same conditions irrespective of whether the amount of the stackedpapers is large or small, and therefore double feed due to an increaseof the amount of stacking of paper can be avoided. Also, since the gateplate is inclined, the paper is more strongly pressed against thecircumferential surface of the first roller by its wedging action, andthe force of paper feeding by the first roller is increased. When thepaper is a thick paper, due to the stiffness of the paper, the force ofpaper driving of this first roller is effectively transferred up to thefront edge part of the paper striking the separation pad. As the paperbecomes thicker, the feed out force of the paper when the front edge ofthe paper strikes the separation pad becomes stronger, and thereforepaper misfeeding during the supply of thick paper can be prevented.

Further, when the inclination angle of the gate plate is made variableand the inclination angle thereof is increased when the paper is thick,the above-described function is exhibited more effectively. When controlis adopted in which the inclination angle of the gate plate is increaseduntil the first paper feed detection sensor arranged between the firstroller and second roller detects the paper, when the paper is easily fedout, the inclination angle of the gate plate is retained as small, whilewhen the paper is difficult to feed out, the inclination angle of thegate plate is increased in accordance with that level of difficulty toincrease the contact force of the paper against the first roller by thewedging action thereof, so that the gate plate is automatically set atan angle at which a necessary and sufficient paper feeding force isgenerated. Note that, when the paper is replaced, the gate plate returnsto the side at which the inclination angle becomes small, and theinclination angle of the gate plate is set according to theabove-described procedures in accordance with the thickness of the newlystacked paper.

According to another aspect of the present invention, as the biasingforce changing mechanism of the paper conveyance spring of the automaticpaper feeding apparatus, a slide cam which slides in adirection parallelto the paper feed rollers is used. Namely, there is adopted aconstruction in which, on the seat plate on which the base end of theconveyance spring is affixed, a guide is provided parallel to the paperfeed rollers, a cam piece abutting against the plate surface of theconveyance spring is provided on the slider slidably fitted on thisguide, and the slider is moved along the guide, whereby the cam piece ismade to abut against or separate from the surface of the spring, therebymaking the biasing force of the conveyance spring variable.

Also, the paper width detection sensor of the image reading apparatus ofthis invention is constructed so as to be attached to the paper feedframe and sensor bracket by a simple construction of fitting in thesensor bracket and sensor arm. Namely, elastic projections provided withengagement claws at the front ends are formed on the attachment surfaceof the sensor bracket so as to project therefrom. Support bearings forsupporting the sensor arm at the shaft are shaped provided with throughholes with recesses having narrower widths than the diameters of thethrough holes. In the shaft support portion of the sensor arm, there isprovided a pivot pin comprised of a cylinder having a diameter whichenables fitting pivotably with the said through hole and having aparallel chamfered portion having a thickness that enables passingthrough the aforesaid recesses. The pivot pin is pivotally supported inthe through-holes.

Also, as the construction for mounting the light source lamps, there isadopted a construction in which projection pieces provided at intervalsin the longitudinal direction of the lamp frame are simply inserted intoslit holes provided in the reading unit frame to secure the lampsthereto.

The biasing force switching mechanism of the conveyance spring in thisinvention changes the biasing force of the conveyance spring withrespect to the paper feed rollers by inserting a cam piece at thesurface of the conveyance spring from the side by sliding the slider andforcibly bending the conveyance spring by the cam piece. When the slideris slid to disengage the cam piece from the spring, the forced bendingforce by the cam piece is released, and therefore the biasing force ofthe conveyance spring returns to its original level. Accordingly, it ispossible to change the biasing force of the conveyance spring bychanging the sliding position of the slider. It is also possible tochange the amount of projection of the cam piece stepwise along thesliding direction of the slider and thereby to change the biasing forceof the conveyance spring in two or three or more stages.

The paper width detection sensor 12 in this invention is attached byrotating the sensor arm 14 a considerable amount in a predetermineddirection around the sensor bracket 13 and in that state inserting thepivot pin 28 thereof into the through holes 21 through the recesses 22,then turning the sensor am in the reverse direction and fitting theprojections of the sensor bracket in the engagement holes of the paperfeed frame.

In the attached sensor, the sensor bracket is engaged with the paperfeed frame by engagement by the claw pieces. The rocking angle of thesensor arm inside the sensor bracket is defined by the abutment of astopper plate, which restricts the insertion of the shielding plate intothe opto-electric sensor housing, and the detection lever against thepaper feed frame. In this rocking range, the angle is never one wherethe parallel chamfered portion of the pivot pin is parallel to therecesses of the through holes, and therefore so long as the sensorbracket is not detached from the paper feed frame, the sensor arm willnot detach from the sensor bracket. The sensor arm and the sensorbracket are attached to the sensor bracket and paper feed frame in asimple manner, therefore the assembly becomes easy, and also the numberof parts becomes small.

Also, according to the attachment structure of the light source lamps ofthis invention, it is sufficient if projection pieces are formed in thatlamp frame on the lamp unit, and it is sufficient if only small slitholes are provided in the reading unit frame. Therefore, theconstruction and the attachment and detachment are extremely easy, andalso the problem of lowering of strength of the frame does not occur. Inthis way, in the above construction for attaching and detaching thelight source lamps, the light source lamps cannot be attached ordetached unless the members arranged above the light source lamps areremoved, and therefore it may be considered that the attachment anddetachment work would be cumbersome, but in practice, to enable clearingof jammed paper in the paper passage, there is adopted a construction inwhich the frame of the apparatus is divided to an upper frame and alower frame, with the members above the document passage are attached tothe upper frame and with the upper frame being pivotally supported bythe lower frame. The document passage is opened by opening the upperframe, and so it is possible to easily insert or remove the light sourcelamps from above when the upper frame is opened.

Also, in the paper passage system of a two-side reading type imagereading apparatus of this invention, a first guide roller and a secondguide roller having white circumferential surfaces are arranged inparallel at the insertion side and feedout side of the documentsandwiching the document reading position therebetween. A transparentguide forming a first arc passage and second arc passage and having atop angle smaller than 90 degrees is provided between the first andsecond guide rollers. The document reversing apparatus is arranged on aside opposite to the transparent guide between the two guide rollers.

Beneath the transparent guide, an imaging lens with a light axisparallel to the feeding direction of the document is arranged. Betweenthis imaging lens and the aforesaid transparent guide, the first lightsource lamp and second light source lamp arranged so as to face thefirst guide roller and second guide roller, respectively; a firstreflection surface facing the second guide roller side and a secondreflection surface facing the first guide roller side; and a mutuallyopposite first sub-reflection surface and second sub-reflection surfaceare arranged, with the first elements and second elements being arrangedon the two sides of the center plane of the transparent guide andimaging lens. The first image sensor and the second image sensor arearranged on the two sides below the imaging lens.

Also, in the paper passage system of the two-side reading type apparatusof this invention, a first reading light L₁ read at a first readingpoint P₁ on the first guide roller side is sequentially reflected at thefirst reflection surface, first sub-reflection surface, and the secondsub-reflection surface, passed through the imaging lens, and focused onthe first image sensor. A second reading light L₂ read at a secondreading point P₂ on the second guide roller side is sequentiallyreflected at the second reflection surface, second sub-reflectionsurface, and first sub-reflection surface, passed through the imaginglens from a direction opposite to the first reading light L₁, andfocused on the second image sensor. The surface of the document fed fromthe first arc passage into the reading portion is read at the firstreading point P₁ while being fed by the guide rollers and notillustrated feed rollers and then is fed out to the reversing apparatus.After the document passes the first reading point P₁, the document isreversed by the reversing apparatus and guided to the second arc passageby the rotation of the second guide roller. Then, the back surface ofthe document is read at the second reading point P₂ while being fed bythe second guide roller.

According to the construction of this invention, it is possible toarrange the first reading point P₁ and the second reading point P₂ closeand, in addition, possible to contain two reading units in a space ofthe same extent as the conventional one reading unit by reflecting thereading lights L₁ and L₂ read at two reading points P₁ and P₂ so thatthey intersect each other. Thus, the apparatus can be constructed in avery small size. Moreover, it is sufficient even .if there is only oneimaging lens. Also, the parts are symmetrically arranged, and thereforealso the cost if the parts and the cost of assembly can be reduced.

Other objects, structures, functions, effects, etc. of the presentinvention will be more apparent from the following explanation of theembodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrative side view showing one embodiment of an imagereading apparatus of this invention;

FIG. 2 is a side view showing a variable angle construction of a gateplate;

FIG. 3 is a perspective view showing the variable angle construction ofthe gate plate;

FIG. 4 is a side view showing one embodiment of a document feedingportion;

FIG. 5 is a side view of a paper separation portion;

FIG. 6 is a plan view of the paper separation portion;

FIG. 7 is a disassembled perspective view of a paper width detectionsensor;

FIG. 8 is perspective view showing another embodiment of a sensorbracket of the paper width detection sensor;

FIG. 9 is a perspective view showing the attachment structure of a lightsource lamp;

FIG. 10 is a side view showing an opening structure of an upper frame;

FIG. 11 is an explanatory view of the attachment method of the lightsource lamps;

FIG. 12 is an explanatory view showing the attachment state of the lightsource lamps;

FIG. 13 is an explanatory view showing the attachment and lock state ofthe light source lamps;

FIG. 14 is a diagrammatical side view of an image reading apparatusaccording to the present invention;

FIG. 15 is a perspective view of a locking mechanism of a frame bodycover;

FIG. 16 is a perspective view of the structural members of the main bodyframe and the frame body cover;

FIG. 17 is a side view of an operation side lock pair;

FIG. 18 is a side view of a reversing operation side lock pair;

FIG. 19 is a side view of one embodiment of the paper guide according tothe present invention;

FIG. 20 is a perspective view showing the symmetrical moving mechanismshown in FIG. 19 taking as an example the second symmetrical movingmechanism;

FIG. 21 is a side view of the locking mechanism part shown in FIG. 19;

FIG. 22 is an enlarged perspective view of a principal part of FIG. 21;

FIG. 23 is a plan view showing the first symmetrical movement mechanismof the paper guide;

FIG. 24 is a side view diagrammatically showing another embodiment ofthe symmetrical movement mechanism;

FIG. 25 is a cross-sectional view showing another embodiment of thelocking mechanism;

FIG. 26 is a cross-sectional plan view showing a further embodiment ofthe locking mechanism;

FIG. 27 is a structural view of the principle of the reading mechanismof a white reference sheet in the image reading apparatus of the presentinvention;

FIG. 28 is a figure showing one embodiment of the concrete structure ofthe apparatus shown in FIG. 27;

FIG. 29 is a flow chart of the white reference setting processing shownin FIG. 27;

FIG. 30 is an explanatory view of the structure diagrammatically showinganother paper feeding mechanism different from that in FIG. 1;

FIG. 31 is an explanatory view of the structure diagrammatically showinganother embodiment from that of FIG. 30;

FIGS. 32A and 32B are side views showing the states before and after thefront edge alignment operation of a stacked large number of documents,respectively;

FIG. 33 is a side view showing an embodiment in which the projectionsare provided in the hopper;

FIG. 34 is a side view showing an embodiment in which the projectionsare provided in the paper feed guide;

FIG. 35 is a figure showing an embodiment in which a sheet materialhaving a charge train close to that of the paper guide is adhered to theguide;

FIG. 36 is a front view showing a reference sheet for performing initialcorrection;

FIG. 37 is a graph showing the relationship between the length of thepaper and the paper feeding speed;

FIG. 38 is a figure showing an example of arrangement of the size sensorof the paper;

FIG. 39 is a graph showing the correction state of the sub-scanningmagnification in accordance with the paper size;

FIG. 40 is a perspective view schematically showing the overall outerappearance of the image reading apparatus according to the presentinvention;

FIG. 41 is a diagrammatical side view showing one example of theconventional two-side reading construction;

FIG. 42 is a diagrammatical side view showing another example of theconventional two-side reading construction;

FIG. 43 is a view explaining the conventional paper feeding mechanism;

FIG. 44 and FIG. 45 are a side view and a plan view of a conventionalpaper separation spring;

FIG. 46 is a perspective view of the conventional paper width detectionsensor; and

FIG. 47 is a side view showing a conventional light source lamp unit.

BEST MODE FOR WORKING THE INVENTION

Note that, in the following explanation as well, parts corresponding tothose in the prior art are indicated by the same numerals for clearerunderstanding, but this does not always mean that the structures areexactly the same.

FIG. 1 is a side view showing one embodiment in which an automatic paperfeeding apparatus of this invention is attached to an image readingapparatus. A first roller 5a of the paper feed rollers 5 is arranged atthe front edge portion of the hopper 3 on which the documents 1 to beread are stacked. A gate plate 57 is arranged at a part against whichthe front edge of the document 1 above this first roller 5a abuts. Thegate plate 57 is provided with an inclination leftward with respect tothe normal of the first roller 5a so that the position is made moreeccentric to the feeding direction (leftward in the figure) as the gateplate 57 is at lower position of the document 1. Between that front end57a and the circumferential surface of the first roller 5a, a slit 58allowing the passing of 10 to 20 sheets of documents is formed. The gateplate 57 of FIG. 1 is of a fixed construction and is attached by beingsecured to the frame of the not illustrated apparatus etc.

A second roller 5b of the paper feed rollers 5 is arranged on thedocument feed-out side of the first roller 5a. The front edge portion ofthe sheet-like separation pad 7B, provided with flexibility, is incontact with the upper portion thereof in a manner curling around thesame. The first roller 5a and the second roller 5b are synchronouslydriven by the transmission gear 18. A plurality of sheets of paperpassed through the slit 58 are guided to the contact portion between thesecond roller 5b and the separation pad 7B by the frictional force ofthe first roller 5a. Only the lowermost sheet of paper is separated andfed out from the front end of the separation pad 7B.

On the extension of the front end of the separation pad 7B, the contactportion between a drive roller 9a and driven roller 9b of the feedrollers 9 is positioned. The paper 1 passing this contact portionchanges in its direction when abutting against a horizontally providedplaten glass 101 and is guided to the contact portion between a driveroller 13a and a driven roller 13b of the eject rollers 13. The readingportion "a" of the document is formed on the platen glass 101, and theimage information of the document in the reading portion a illuminatedby the light source lamp 25 is read by the light receiving cell of theCCD 33 through a reflection mirror 27 and an imaging lens 31. A whitereference sheet 29 setting the reading level of the CCD 33 is adhered tothe upstream side from "a" of the reading portion of the platen glass101. The paper feed roller 5, feed roller 9, and the eject roller 13 aresynchronously driven by a feed motor 51 via transfer gears 4 and 6indicated by a broken line in the figure. The rotation of the feed motor51 is transferred via the first transmission gear 4 to the drive roller9a of the feed rollers, and that rotation is transferred via the secondtransmission gear 6 and the one-directional clutch 20 to the driveroller 13a of the eject rollers 13. This one-directional clutch is forpreventing the rotation of the feed rollers 9 from being transferred tothe eject rollers 13 when the feed rollers 9 rotate in reverse. When thedrive roller 9a of the feed rollers rotates in the forward direction,that is, in the clockwise direction in FIG. 1, the relatedone-directional clutch 20 is connected and the eject rollers 13 rotatein the same direction, while when the feed rollers 9 rotate in reverse(in the counterclockwise direction of FIG. 1), the connection of theone-directional clutch is released, and the eject rollers 13 are kept intheir stopped state.

The second roller 5b of the feed rollers 5 is connected to the firsttransmission gear 4 via the one-directional clutch 22. Due to the factthat the drive roller 9a of the feed rollers is in contact with thepaper at the bottom part and the paper feed rollers 5 are in contactwith the paper at the top part, the feed rollers 9 and the paper feedrollers 5 are driven in a reverse direction to each other inrelationship with respect to that paper. The one-directional clutch 22interposed between the first transmission gear 4 and the second roller5b is connected when the feed roller 9 rotates in the reverse direction,that is, in a direction feeding back the paper, to rotate the paper feedroller 5 in a forward direction, that is, in a direction feeding out thepaper. When the feed roller 9 rotates in the forward direction, theconnection of the related clutch is released, and the paper feed roller5 is kept in a free rotation state. The second paper feeding detectionsensor 103 is attached between the second roller 5b and the feed roller9 and a paper rear edge detection sensor 105 is attached to the positionimmediately upstream of the reading portion "a".

Note that the first and second clutches 22 and 24 are provided on therotation shafts of for example the second transmission gear 6 and thesecond roller 5b, respectively, and that it is assumed that theabove-described rollers and gears are connected by gears (notillustrated) having the same diameter as those of the respectiverollers. Note, naturally the present invention is not restricted tothis.

An explanation will be made next of a paper feeding operation of theapparatus of FIG. 1. After the documents are placed on the hopper 3, thefeed motor 51 is rotated in a direction of reverse rotation of the feedrollers 9. At this time, the first roller 5a and second roller 5b of thepaper feed rollers 5 rotate in synchronization in a direction feedingout the paper. First, the first roller 5a feeds out a plurality ofsheets (for example 10 to 20 sheets) of paper primarily separatedthrough the slit 58 between the same and the gate plate 57 to a spacebetween the second roller 5b and the separation pad 7B, subsequently thelowermost one sheet of paper separated by the second roller 5b and theseparation pad 7B is fed out to the feed rollers 9 in a state where bentslightly downward along the circumferential surface of the second roller5b. Then, after the front edge of the fed out paper is detected by thesecond paper feeding detection sensor 103, the feed motor 51 is furtherrotated exactly by a preliminarily set pulse number, and the front edgeof the fed out paper is made to abut against the nip portion of the feedrollers 9, to slightly bend the same between the feed rollers 9 and thefront end of the separation pad 7B. Then, the feed rollers 9 are rotatedforward. The front edge of the paper fed out by this operation isaligned in a direction parallel to the shaft of the feed roller 9, thatis, the skew is corrected, and the paper is fed to the reading portion"a" in a state where gripped by the feed rollers 9. At this time, thepaper feed rollers 5 are in a free rotation state due to the action ofthe one-directional clutch 22 interposed between the first transmissiongear 4 and the second roller 5b. The two rollers 5a and 5b rotate at aspeed according to the movement of the paper fed by the feed rollers 9.

When the paper fed into the reading portion "a" is further fed andgripped by the eject rollers 13 and the rear edge of the paper isseparated from the feed rollers 9 and reaches the position of the paperrear end detection sensor 105, the rotation of the feed motor 51 isreversed again at this position. By this operation, the next paper onthe hopper 3 is fed out toward the feed rollers 9. When the feed rollers9 are switched to the forward rotation side again, also the ejectrollers 13 start rotation in the forward direction again and feed outthe previous paper to the stacker 15 (FIG. 50). In this way, the sheetsof paper stacked on the hopper 3 successively pass through the readingportion "a" in a state with an interval equal to the distance betweenthe feed rollers 9 and the paper rear edge detection sensor 105 isformed and are ejected to the stacker.

FIG. 2 and FIG. 3 show an example in which the gate plate 57 of theembodiment of FIG. 1 is given a variable angle construction. The gateplate 57 is secured to the front end of a bent arm 24 of a support shaft8 rotated by a gate opening and closing motor 10. By rotating the gateopening and closing motor 10 in the forward and reverse directions, thegate plate is moved in inclination as shown in FIG. 2 about the supportshaft 8 as the center. The support shaft 8 is preferably set at aposition so that the clearance of the slit between the front end of thegate plate 57 and the first roller 5a is slightly enlarged when the gateplate 57 is turned in a direction increasing the inclination angle ofthe gate plate 57. The amount of change of the clearance of the slit 58when the gate plate 57 is moved in inclination can be appropriately setby the length of the arm 24. The reference inclination angle of the gateplate 57 can be detected by a home position detection sensor (opticalsensor) 26 shown in FIG. 3. The reference angle of the gate plate 57 isset at the position at which the gate plate 57 is the most vertical.Between the first roller 5a and the second roller 5b, a first paperfeeding detection sensor 107 detecting the feeding of the paper from theslit 58 is provided. An empty sensor 109 detecting the presence orabsence of the paper on the document stand is provided on the hopper 3.Note that the above-described sensors may be well known ones. Also, thedetection signals thereof are sent to the controller 100.

An explanation will be made next of an angle setting operation of thegate plate 57 of FIGS. 2 and 3. In an initial state where the emptysensor 109 detects the absence of paper, the gate plate is set at theinitial position which is detected by the home position detectionsensor. This initial position is a position at which the inclinationangle of the gate plate 57 becomes smallest.

When sheets of paper are carried on the hopper 3 and the paper feedroller 5 is rotated, if the carried paper is easily fed paper, even ifthe inclination angle of the gate plate 57 is small, the paper is fedout through the slit 58, this is detected by the first paper feedingdetection sensor 107, and no rocking operation of the gate plate 57occurs. On the other hand, when the paper is difficult to feed paper,even if the first roller 5a is rotated in this state, the paper is notfed out. At this time, the first paper feeding detection sensor 107 doesnot detect paper even when a certain time elapses after the first roller5a is rotated, and therefore a rotation instruction is given to the gateopening and closing motor 51 from the controller 100, and the gate plate57 is rocked in a direction increasing the inclination angle exactly bya preliminarily set amount. When the first paper feeding detectionsensor 107 does not yet detect paper after waiting for a predeterminedtime again, the rotation instruction is given again from the controller100 to the gate opening and closing motor 51, and the gate plate 57 isfurther inclined. In this way, when the inclination angle of the gateplate 57 is increased, the abutment force between the paper and thefirst roller 5a is increased by the wedging action thereof, andtherefore the paper starts to be fed out from the slit 58 at a certainpoint of time. By this, that paper is detected by the first paperfeeding detection sensor 107. Thereafter the first paper feedingdetection sensor 107 continuously detects the paper until the feeding ofall paper is ended, and therefore the gate plate 57 retains the anglewhen the supply of the paper is initially started, so the angle of thegate plate is automatically set in accordance with the nature of thepaper. Then, when the documents 1 are all supplied and the absence ofthe paper is detected by the empty sensor 109, the instruction forrotation instruction in the reverse direction is given to the gateopening and closing motor 51, to restore the angle of the gate plate 57to the reference angle.

According to this invention explained above, the settability of thedocuments on the hopper is enhanced. Even if the documents are casuallyset, a stable paper feeding performance can be obtained, and the workingload of the operator can be reduced. Also, it becomes possible toincrease the amount of stacking of the paper on the hopper. Theautomatic feeding of documents having a paper thickness which wasimpossible in the conventional bottom take-out type becomes possible.Also, the fluctuation of the relationship of force between the paperfeeding force and resistance at the paper separation portion is small,and therefore a stable paper feeding performance is exhibited withrespect to all paper.

Also, in the case of a construction with a variable angle of the gateplate, by changing the angle of the gate plate, feeding becomes possiblewithout paper misfeeding of thick paper documents due to the wedgingeffect. At the same time, by changing the gate gap, double feed producedby a large number of thin paper documents being taken into theseparation pad portion can be prevented.

Also, by adopting a connection construction in which the feed roller andthe supply roller are rotated in a reverse direction from each other viaa one-directional clutch, paper skewing is reduced by the front edgealignment function, and the through-put can be improved by improvementof the paper feeding speed.

The two-side reading type apparatus shown in FIG. 4 will be explainedlater.

FIGS. 5 and 6 show the paper separation portion of a bottom take-outtype automatic paper feeding apparatus of the image reading apparatus ofthis invention. As mentioned before, the paper feed roller 5 is rotatedcounterclockwise in FIG. 5 by the drive mechanism shown in FIG. 1 andfeeds out the lowermost sheet of the documents, which are insertedstacked between the paper feed roller 5 and the conveyance spring 7,leftward in the figure. As shown in the plan view of FIG. 6, in theconveyance spring 7, two fixed separation springs 7a and moveableseparation springs 7b formed in a thin and long tongue piece areprovided on the seat plate 115 while fixing the base ends on the seatplate 115 in the document width direction.

A rectangularly shaped guide hole 116 which is long in the documentwidth direction is provided on the seat plate 115. A slider 117 isattached to a guide hole 116 thereof so that it can freely slide in thelongitudinal direction. Arms 118 are provided at the slider 117 so as tobe projected therefrom at the same interval as the interval of the twomoveable springs. Cam pieces 119 are provided at front ends of thesearms 118. The cam piece 119 intrudes to the bottom of the moveablespring 7b so as to push the surface of the moveable spring 7b on theright side of FIG. 5 when the slider 117 on the figure is moved upwardfrom the state of FIG. 6 and gives an abutment force in a directionseparating the front end of the moveable spring 7b from the paper feedroller 5.

Accordingly, when the slider 117 is gripped by the fingers and movedupward in FIG. 6, the moveable spring 7b is separated from the paperfeed roller 5 and the biasing force of the spring as a whole becomesweak. When the slider 117 is moved downward in FIG. 6, the cam piece 119is detached from the moveable spring 7b and the moveable spring 7b iselastically pressed against the paper feed roller 5. Therefore, thebiasing force of the spring 7 as a whole becomes large. The biasingforce of the spring 7 is adjusted in accordance with the quality ofpaper of the document by setting things so that the biasing force of thespring 7 is made large when the paper of the document is thick and sothat the biasing force of the spring 7 is made small when the paper ofthe document is thin.

FIG. 7 shows the document width detection sensor (corresponding to thesensor 35 of FIG. 1) improved by the present invention. The paper widthdetection sensor comprises three members of an opto-electric sensor 122accommodated in a U-shaped housing 121, a sensor bracket 123, and asensor arm 124. The sensor bracket 122 and the housing 121 thereof arewell known. The sensor bracket 123 is formed in the shape of a frame andhas two projections 125 projecting out on the attachment surface 141side thereof. Claw pieces (hooks) 126 facing outward are integrallyformed at the front ends of the projections 125. Slit holes 128 areformed in the frame 100 of the automatic paper feeding apparatus atpositions corresponding to the projections 125. Recesses 129 for givinga flexible elasticity to the projections 125 are provided at the rootportions of the projections 125. Through holes 131 are provided in thepair of projecting bearing portions of the sensor bracket 123 on thesame axial lane. Recesses 132 having narrower widths than the diametersof the penetration holes 131 are provided so as to open the sides of thepenetration holes 131.

The sensor arm 124 is a seesaw lever-shaped arm integrally provided witha shielding plate 133, a stopper plate 134, and a detection lever 135similar to those of the conventional construction. Supporting pins 138having a shape obtained by chamfering in parallel the circumferentialsurface of a cylinder having a smaller diameter than the diameter of thepenetration hole 131 by exactly the amount of the free gap to athickness slightly narrower than the width of the penetration hole 131are integrally formed on the two ends of that bearing portion 136 sothat the direction of the parallel chamfered portion 139 and thedirection of the recess 132 become different when the sensor arm 124 isattached to the sensor bracket 123. The sensor arm 124 is inserted fromthe recess 132 into the penetration hole 131 while matching thedirections of the parallel chamfered portion 139 and recess 132 in astate where the sensor arm 124 is rotated in the counterclockwisedirection by about 135 degrees from a state shown in FIG. 7 and pivotedin the clockwise direction thereat, whereby it is axially supported inthe penetration hole 131.

In this way, when the projections 125 are inserted into the slit holes128 and the sensor bracket 123 is attached to the frame 100 of theautomatic paper feeding apparatus after the sensor arm 124 is axiallysupported by the sensor bracket 123, the pivoting of the sensor arm 124in the clockwise direction of the figure is limited by abutment of thestopper plate 134 against the top surface of the housing 121 of theopto-electric sensor, and the pivoting in the counterclockwise directionin the figure is limited by abutment of the detection lever 135 againstthe frame 100 of the automatic paper feeding apparatus, therefore astate where the direction of the parallel chamfered portion 139 of thesupporting pin 138 and the direction of the recess 132 of the sensorbracket coincide cannot be exhibited. Accordingly, the sensor arm 124will never drop out. Note that, in this state, the shielding plate 133cuts off the light path of the opto-electric sensor 122. When thedocument abuts against the detection lever 135 from the directionindicated by an arrow A of the figure, the sensor arm 124 pivots in thecounterclockwise direction of the figure, and the shielding plate 133retracts from the light path of the opto-electric sensor 122, andtherefore the abutment of the document against the detection lever 135can be sensed by this. By arranging a plurality of such detectionsensors in the direction of width of the document, the paper width ofthe fed documents an be detected by a combination of ON and OFF signalsthereof.

Note that, FIG. 8 shows another embodiment of the sensor bracket, inwhich the rattling between the sensor bracket and the paper feed frame100 when the former is attached to the latter can be further reduced.The sensor bracket 123A of this embodiment is provided with projections125A for insertion through the slit holes provided in the paper feedframe on the attachment surface 141 side thereof at four portions, andprovided with claw pieces 126A and 126A in two directions orthogonal toeach other, thereby absorbing the rattling in two directions in theupper surface of the frame of the automatic paper feeding apparatus. Therest of the structure is similar to that of FIG. 7.

FIG. 9 shows an improved structure of attachment of a light source lamp25 in the image reading apparatus of this invention, which has a simpleshape in which projection pieces 173 are formed on the two sides of thelongitudinal direction of the plate-shaped lamp frame 172 provided withsockets 171 for the light source lamp on the two ends in thelongitudinal direction. The projection pieces 173 are inserted into theslit holes 175 provided in the frame 174 of the reading unit to supportthe light source lamp 25. As mentioned before, according to such aconstruction, as shown in FIG. 10, by opening the upper portion frame176 of the image reading apparatus around the pivotally support shaft177, attachment and detachment of the light source lamp 25 can be easilycarried out. Also, the problem of the working space at the replacementof the light source lamp, the problem of reinforcing of the frame 174,etc. can be avoided.

FIG. 11 through FIG. 13 show another attachment construction of thelight source lamp 25. On the back surface side (reverse light sourcelamp side) of the plate-like lamp frame 172, two engagement projectionpieces 173A and 173A having grips 208 and 209 at the upper end arearranged at an interval between them. The engagement projection piece173A on the left side is secured by a screw 213, and the engagementprojection piece 173A on the right side is pivotally attached by a screw214 attached with a spacer. An elongated hole 215 is provided in theengagement projection piece 173A on the right side in the vicinity ofthe screw 214. Into this elongated hole 215, a pin 216 implanted in thelamp frame 172 so as to stand up is inserted and engaged therewith. Thispin 216 regulates the pivoting angle of the engagement projection piece173A. Reference numeral 217 is a connector secured to the bottom side ofthe lamp frame 172. On the other hand, the frame 174 of the reading unitis provided with slit holes 175A and 175A into which the engagementprojection pieces 173A and 173A are inserted and a connector 218 fittedon the connector 217. A plate spring 219 biasing the front end of theengagement projection piece 173A to be inserted in the engagementdirection (counterclockwise direction of FIG. 13) is provided on thelower surface of the slit hole 175A on the right side. Note that, it ispossible to replace the plate spring 219 by a tongue piece integrallyformed with the frame 174 of the reading unit by shaping in the vicinityof the slit hole 175A.

For attachment of the lamp frame 172 to the frame 174 of the readingunit, the engagement projection piece 173A on the left side is insertedinto the slit hole 175A on the left side, the engagement projectionpiece 173A on the right side is pushed into the slit hole 175A on theright side against the plate spring 219 by pivoting in the clockwisedirection of the figure with the abutment portion P between theengagement projection piece 173A and the frame 174 of the reading unitas the center. At this time, the two connectors 217 and 218 are fittedwith each other, to determine the relative position between the lampframe 172 and the frame 174 of the reading unit. The engagementprojection piece 173A on the right side of the positioned lamp unit 172is pivoted in the counterclockwise direction in the figure by the platespring 219 and engaged with the frame 174 of the reading unit to makethe locked state of the lamp frame 172 more secure in association withthe engagement projection piece 173A on the left side. When adoptingsuch an attachment construction, it is possible to reliably prevent thedetachment of the lamp frame by shock or vibration occurring duringtransportation etc. Also, when the lamp frame 172 is detached, if thegrip 208 of the engagement projection piece on the left side is graspedby the left hand and the grip 209 of the engagement projection piece onthe right side is grasped by the right hand so as to move the sameupward, the engagement projection piece 173A on the right side pivotscounterclockwise against the plate spring 219, and the engagement stateis released, and therefore the detachment can be easily performed bypulling this upward in this state. Thus, also the problem of the workingspace at the replacement of the light source lamp and problem ofreinforcing of the frame 174 etc. can be avoided.

According to this invention explained above, it is possible toconstitute the image reading apparatus of a data processing apparatuswith a remarkably smaller size in comparison with this type ofconventional apparatus and to provide the apparatus at a lower cost bythe reduction of the fabrication steps of parts and assembling steps.

FIG. 4 is a side view showing an improvement of a reverse readingportion 167 of the image reading apparatus of this invention. On theupstream side and downstream side of the document passage, a first guideroller 143 and a second guide roller 144 having a white circumferentialsurface having the same shape are provided so that it can rotate in theclockwise direction of the figure by a not illustrated drivingmechanism. A guide 145 comprising a transparent body of a trapezoidalcross-section having an arc slope on the two sides is provided beneaththe guide rollers 143 and 144. Arc passages 146 and 147 through whichthe documents pass are formed between this transparent guide 145 and theguide rollers 143 and 144. Beneath of the guide rollers 143 and 144, afirst light source lamp 25a is arranged opposite to the first guideroller 143, and a second light source lamp 25b is arranged opposite tothe second guide roller 144. At an intermediate position of these twolight source lamps 25a and 25b, a reflection body 153 provided with afirst reflection surface 151 and a second reflection surface 152 arearranged. The first reflection surface 151 of the reflection body 153 isdirected to the second guide roller 144 side, and the second reflectionsurface 152 is directed to the first guide roller 143 side.

The transparent guide 145 and the reflection body 153 have ahorizontally symmetrical cross-sectional shape. The plane serving as thecenter of the symmetry is arranged so as to match with the synmetricalplane passing through the center of the two guide rollers 143 and 144.Beneath the reflection body 153, an imaging lens 31 with an optical axiswhich is the feeding direction of the document is arranged. Atsymmetrical positions with respect to the aforesaid symmetrical planeabove and below this imaging lens 31, first and second sub-reflectionsurfaces 155 and 156 and first and second image sensors 33a and 33b arearranged so as to schematically face each other.

On the other hand, between the first guide roller 143 and the secondguide roller 144, a pair of gripping rollers 163 comprising two rollers161 and 162 which abut against each other and supported at the shaft ina free rotation state is provided so as to make that one roller 161 abutagainst the circumferential surface of the second guide roller 144.Above the second guide roller 144, an inversion stand 164 extending inthe feeding direction of the documents fed out from the first guideroller 143 is provided. The document gripping portion of the grippingroller pair 163 is arranged at a position receiving the document fed outfrom the first guide roller 143. A switching lever 165 driven by asolenoid is arranged directly above the grasping roller pair 163 so thatit can swing around the above supporting pin 166.

In the structure of the figure, when the document is supplied to thefirst arc passage 146 between the first guide roller 143 andthe-transparent guide 145 from the right of the figure by the rotationof the first guide roller 143 and the feed roller 5 (FIG. 1) provided onthe upstream side of the first guide roller 143, the document is bentinside the first arc passage 146 and fed out toward the gripping rollerpair 163. When the document passes through the first arc passage 146,the front surface thereof is read at the first reading point P₁. Thereading light L₁ of the first reading point P₁ is reflected at the firstreflection surface 151 of the reflection body, the first sub-reflectionsurface 155, and the second sub-reflection surface 156, passes throughthe imaging lens 31 from the right side to the left side in the figure,and is read by-the first image sensor 33a arranged on the left side ofthe figure of the imaging lens 31.

The document fed out from the first arc passage 146 is pulled up to theleft top of the figure while being gripped by the gripping roller pair153. At the time at which the rear edge of the document passes thegripping roller pair 163, the switching lever 165 pivots clockwise inthe figure and feeds the document fed into the reversing apparatus 167to a space between the second guide roller 144 and the roller 161abutting against this. The fed document is fed out downward while beinggripped between the second guide roller 144 and the roller 161 abuttingagainst this, is guided by the not illustrated guide along thecircumferential surface of the second guide roller 144, and is fed intothe second arc passage 147.

Then, the back surface of the document is read at the second readingpoint P₂ provided immediately before the document is fed into thissecond arc passage 147. The reading light L₂ of the second reading pointis reflected at the second reflection surface 152 of the reflectionbody, is reflected at the second sub-reflection surface 156 and thefirst sub-reflection surface 155, passes through the imaging lens 31from the left to the right of the figure, and is read by the secondimage sensor 33b arranged on the right side of the imaging lens 31. Thedocument passes through the second arc passage 147 and is fed out to thestacker side on the left side of the figure while the back surface isbeing read in this way.

In the construction of the figure, the subsequent document can be fedupward by gripping the same by the gripping roller pair 163 constitutedby the rollers 161 and 162 while feeding the previous document downwardby gripping the same by the second guide roller 144 and roller 161.Therefore, processing so that the documents are successively fed intothe reading portion and the front surface of the subsequent document canbe read while performing the reading of the back surface of the previousdocument, so it is possible to read a large number of documents at ahigh speed by using the automatic paper feeding apparatus incombination.

Also, as apparent from the figure, it is possible to make the entireapparatus very compact, two reading lights L₁ and L₂ can be focused totwo image sensors 33a and 33b by one imaging lens 31, and the shape andarrangement of the members are symmetrical, therefore the fabricationand assembly of parts are easy and also the assembly precision can bemade correct.

FIG. 14 to FIG. 18 show an embodiment concerning an improvement of thelocking mechanism of the frame body cover in the image reading apparatusof the present invention.

As shown in FIG. 14, the frame body cover 212 covering the paper passage23 of a document feeding type document reading apparatus must beconstructed to allow removal of the document without tearing when paperclogging occurs. For this reason, there is adopted a construction inwhich one of the separation roller 5 and the separation pad 7 arrangedso as to face each other sandwiching the paper passage 23 therebetween,one of the optical reading unit 21 and the document backup member 211arranged so as to face each other sandwiching the reading portion "a"therebetween, one of the side rollers 9a and 13a of the feed rollers 9and 13, etc. are attached to the frame body cover 212 side. When theframe body cover 212 is opened, the paper passage 23 is almostcompletely opened.

In such a construction, when the frame body cover 212 is closed, it isnecessary to correctly regulate the interval between the backup member211 and optical reading unit 21 of the reading portion. For example, thepositioning projections 217 and 218 regulating the position of theintermediate portion between the reference platen plane of the platenglass 101 or the like and the frame body cover 212 are provided on thetwo sides of the frame body cover 212. The frame body cover 212 isprovided so that it can be freely opened or closed in such a manner thatusually the base end is pivotally supported around the main body frame200. Therefore the locking pairs 236 and 237 locking the frame bodycover 212 to the main body frame 200 in the closed state is provided atthe front end of the frame body cover 212. The paper passage 23 isopened between the frame body cover tip and the main body frame, andtherefore there adopted a construction for this lock pair in which theframe body cover 212 and the main body frame 200 are stopped byengagement on the two sides of the front end of the frame body cover212.

The lock pairs 236 and 237 provided on the two sides of the front end ofthe frame body cover 12 are constituted by hooks 221 and 222 andengagement pins 227 and 228 engaged with them. Springs 229 and 230 areprovided biasing the hooks 221 and 222 in the locking direction.

It is also possible to individually operate the hooks 221 and 222 of thelock pairs 236 and 237 provided on the two sides of the front end of theframe body cover 212, but it is convenient if, as shown in FIG. 15,hooks 221 and 222 on the two sides are connected by the connection shaft219, the operation lever 223 is provided only in one hook 221, and therelated operation lever 223 is operated, whereby the engagement anddisengagement of hooks 221 and 222 on the two sides are simultaneouslycarried out.

However, the closing position of the frame body cover 212 is defined bythe positioning projections 217 and 218 provided on the two sides of theintermediate portion of the frame body cover, and therefore where aconstruction is adopted in which the hooks 221 and 222 on the two sidesare connected by a connection shaft 219, if there is an error in thepositional relationship of the hooks 221 and 222 and the engagement pins227 and 228, the operation of the hooks 221 and 222 stops in a statewhere only one of the hooks 221 and 222 is engaged with the engagementpin 227 or 228 thereof, to cause rattling in one engagement portion ofthe lock pair 236 and 237. For this reason, work of adjusting either ofthe hooks 221 and 222 or the engagement pins 227 and 228 so as not tocause rattling in the lock pairs 236 and 237 at the two sides at theassembly of the apparatus and of adjusting so that the lockingoperations of the lock pairs on the two sides are simultaneously carriedout with a uniform force becomes necessary. Therefore, in the presentinvention, so as to make such positional adjustment work of the lockpairs on the two sides at the assembly of the apparatus unnecessary soas to reduce the number of assembly steps, a free clearance 226 isinterposed between the connection member 219 connecting the hooks 221and 222 on the two sides and at least one of the hooks, i.e., 222, andthe engagement surface 235 of the hook 222 on the side at which the freegap 226 is interposed is used as the wedging surface.

According to this, when the frame body cover 212 is closed, even in acase where there is deviation in the relative positional relationshipbetween the hooks 221 and 222 of the lock pairs 236 and 237 on the twosides and the engagement members 227 and 228, the hooks 221 and 222 onthe two sides can solely operate only by the amount of the freeclearance 226 provided between the connection member 219 and the hook222. The operation force thereof is given by the lock springs 229 and230 provided individually in the hooks 221 and 222, and therefore theengagement of the lock pairs 236 and 237 at the two sides is reliablycarried out.

The fitting force between the hook 222 on the reverse operation leverside provided with the free clearance 226 and the engagement member 228is determined to a certain extent by the inclination angle of theengagement surface 235 as the wedging surface of the related hook andthe biasing force of the lock spring 230 thereof. Therefore, it becomespossible to set with what proportion the biasing force of the spring 213biasing the frame body cover 212 in an opening direction is shared bythe lock pairs 236 and 237 on the two sides by the inclination angle ofthe engagement surface 235 of the hook 222 on the reverse operation sideand the biasing force of the lock spring 230.

Also, where the biasing force of the spring 213 biasing the frame bodycover 212 in the opening direction is made to act upon the center of theframe body cover 212, the inclination angle of the engagement surface235 of the hook 222 on the reverse operation lever side and the biasingforce of the lock spring 230 on the related side are determined so thatthe lock pairs 236 and 237 on the two sides share each about half of thebiasing force of the above-described spring 231. However, morepreferably, the biasing force of the spring 213 biasing the frame bodycover 212 in the opening direction is made to act upon the side at whichthe hook 221 directly operated by the operation lever 223 in aneccentric manner is provided, to reduce the locking force applied uponthe hook 222 on the reverse operation lever side. The depressionoperation of the frame body cover 212 at the opening and closing of theframe body cover and the engagement and disengagement operations of thehooks 221 and 222 become smoother.

The motion of the operation lever 223 when the pair of lock 236 and 237is released is transferred to the hook 222 on the reverse operationlever side with a delay of exactly the amount corresponding to the freeclearance, but it is sufficient if the amount of operation of theoperation lever 223 is increased by exactly the amount of the freemovement of the free clearance 226. It is sufficient if this freeclearance 226 has a size that can absorb the assembly error of the lockpairs 236 and 237 of the two sides, and therefore an increase of theamount of operation of the operation ever 223 is not a problem.

Below, a further detailed description will be made of the constructionof the embodiment shown in FIGS. 14 to 18.

As shown in FIG. 14, a platen glass 101 guiding the lower surface of thedocument at the reading portion "a" is secured to the main body frame200 and the optical reading unit 21 is positioned beneath this platenglass 101. In the main body frame 200, along the paper passage 23, theseparation roller 5, the driven side roller 9b of the feed roller 9, andthe driven roller 13b of the eject roller 13 are attached at the shaft;the frame body cover 212 (corresponding to the frame 176 of FIG. 10) ispivotally supported by the main frame 200 by the supporting shaft 213(corresponding to the shaft 177 of FIG. 10). To this frame body cover212, the separation pad 7 opposite to the separation roller 7, the driveside roller 9a of the feed rollers 9, and the drive side roller 13a ofthe eject rollers 13 are respectively attached.

On the two sides of the center portion of the frame body cover 212 inclose contact with the reading portion "a" of the paper, positioningprojections 212 and 218 (FIG. 16) abutting against the upper surface ofthe platen glass 101 are provided. Also, at the front end of the framebody cover 212, the connection shaft 219 parallel to the supportingshaft 213 is pivotally supported at the shaft. To the two ends of thisconnection shaft 219, hooks 221 and 222 on the two sides of the lockingapparatus stopping the frame body cover 212 and the main body frame 200by engagement are attached.

As shown in FIG. 15, the hook 221 at the front side among the hooks 221and 222 is defined as the operation side hook, an operation lever 223 isformed integrally with this hook 221, and the hook 221 is secured to theconnection shaft 219 by the fixing screw 224. The connection shaft 219is made a D-cut shaft with a flat plane formed at one portion on itscircumference as shown in FIG. 17. The hook 222 on the reverse operationside is attached in a state where a free gap 226 which can slightlyfreely pivot is provided around the connection shaft 219 as shown inFIG. 18. The hooks 221 and 222 are shaped so that they are engaged withthe engagement pins 227 and 228 implanted in the main body frame so asto stand up. Locking springs 229 and 230 individually biasing the hooks221 and 222 in the directions for being engaged with the engagement pins227 and 228, respectively, are provided.

As a spring for biasing the frame body cover 212 in the openingdirection around the supporting shaft 213, a torsion bar 231 shown inFIG. 16 is used. The base end of this torsion bar is stopped byengagement at the main frame 200, and the other end (functional end) isstopped by engagement at the rib 32 on the operation hook 221 side ofthe frame body cover 212, which gives a biasing force eccentric to theoperation hook 221 side of the frame body cover 212.

The operation side hook 221 is shaped so that, as shown in FIG. 17, theengagement surface 234 engaged with the engagement pin 227 is a surfacein the tangential direction at the pivoting of the hook 221. Theengagement surface 234 and the engagement pin 227 reliably abut againsteach other by the biasing force of the torsion bar 231. On the otherhand, the engagement surface 235 of the hook 222 on the reverseoperation side serves as the wedging plane as shown in FIG. 18. Alocking force caused by the wedging action is produced between thewedging plane 235 and the engagement pin 223 by the biasing force of thelock spring 230 biasing this hook 222 in the locking direction.

Accordingly, in the closed state of the frame body cover 212, the framebody cover 212 is positioned by three points of the positioningprojections 217 and 218 on the two sides of the intermediate portionthereof and the lock pair 236 of the operation side. The biasing forceof the torsion bar 231 acting while being eccentric to the operationlever 223 side is received by the engagement of the operation side lockpair 236. Then, the lock pair 237 on the reverse operation side absorbsthe position error existing between the two lock pairs 236 and 237 bythe inclination of the wedging plane 235 of the hook and the freeclearance between the gap between the connection shaft 219 and the hook222. The locking force produced by the wedging action based on theinclination of the wedging plane 235 of the hook and the biasing forceof the lock spring 230 functions to reliably make the positioningprojection 217 on the reverse operation lever side to abut against theplaten glass 101, to stabilize the closed state of the frame body cover212 and, at the same time, correctly regulate the positionalrelationship between the frame body cover 212 and the main body frame200 at the reading portion "a".

EFFECT OF THE INVENTION

According to the construction shown in FIG. 14 to FIG. 18, it becomesunnecessary to adjust the positional relationship of mutually engagingelements of the lock pairs provided on the two sides of the front endportion of the frame body cover, and the number of the assembly stepscan be reduced. Also, the opening and closing operation of the framebody cover can be carried out on one side of the frame body cover. Theoperability at the opening and closing of the frame body cover in theapparatus in which the frame body cover is provided so as to belaterally opened is improved. Further, it is possible to set the biasingforce of the opening spring of the frame body cover and the lockingforce of the lock pairs on the two sides with a good balance, and thepositional relationship between the frame body cover and the main bodyframe in the document reading portion can be correctly regulated.

FIGS. 19 to 26 show an embodiment directed to an improvement of thepaper guide mechanism provided in the hopper.

In the image reading apparatus of the present invention, use is made ofa paper guide guiding the paper in a state where the center thereof ismade coincident with the center thereof, the hopper (document stand), orthe paper passage (with a so-called center reference). An explanationwill be made below of an apparatus for adjusting the position of thatguide in accordance with the width dimension of the paper.

In the paper guide guiding the paper with the center reference, it isnecessary to move the paper guides on the two sides symmetrically withthe center of the paper stand or paper passage when the width of theused paper is changed. If the construction is one in which the paperguides on the two sides must be individually set, the work for settingthe paper guide becomes cumbersome.

Therefore, there is conventionally adopted a construction in which thepaper guides on the two sides are connected by a symmetrical movementmechanism utilizing a rack and pinion mechanism or winding transmissionmechanism so that when either one of the paper guides is operated, theother paper guide symmetrically moves.

Nevertheless, the paper guides act to regulate the position of the paperin the width direction, and therefore guides which easily move cannotperform the function of guides. For this reason, useless movement of thepaper guides is prevented by utilizing the friction with the paper standor the like, but if the frictional force is made excessively large,force becomes necessary for the movement of the paper guides when thepaper width is changed. Particularly when the guide width is to be setby operating only the paper guide on one side, the paper guide is movedin inclination due to deviation between in the line of action of theoperating force transferred via the symmetrical movement mechanism tothe paper guide on the opposite side and the frictional force, so thatsticking occurs between the same and the immoveable member guiding this,whereby smooth movement of the paper guide is frequently inhibited.Moreover, the retention of position by the frictional force isinsufficient in stability, and therefore a case where the paper guidesopen during use due to vibration etc. frequently occurs.

Therefore, consideration may be given to a construction in which alocking mechanism is provided in the paper guides so that when thelocking releasing piece adjacent to the guide wall of the paper guide isgripped, the locking is released to enable movement of the paper guidesin the width direction. In paper guides with the center reference,however, where the locking releasing piece is provided at only one paperguide, the paper guide cannot be positioned unless the paper guide onthat side is operated. When locking releasing pieces are provided at thepaper guides on both sides, the paper guide cannot be positioned unlessthe paper guides on both sides are simultaneously operated. Thus, thisis inconvenient.

Therefore, the present invention provides paper guides with a centerreference designed to hold the set position of the paper guides by alocking mechanism, wherein provision is made of an interval settingapparatus wherein simultaneous positioning of the paper guides on thetwo sides is enabled by the operation of either one of the lockingreleasing pieces provided at the paper guides on the two sides.

In FIGS. 19 to 23, the locking releasing pieces 306 a and 306b releasingthe lock of the paper guides are provided at the paper guides 301a and301b at the two sides connected by a symmetrical movement mechanism 304.The locking releasing pieces 306a and 306b on the two sides areconnected by a second symmetrical movement mechanism 314 which is thesame type as the above-described symmetrical movement mechanism 304. Thelocking releasing pieces 306a and 306b are biased in the lockingdirection of the locking mechanism 317 by a spring (plate spring) 307.The symmetrical movement mechanism 304 and the second symmetricalmovement mechanism 314 are provided in a parallel arrangement in astacked state on each other so that they can independently move fromeach other.

As the symmetrical movement mechanisms 304 and 314, a rack and pinionmechanism shown in the following embodiment and the winding transmissionmechanism can be mentioned as an example. They are constructed so thatlinear movement members 302, 312, 323, and 324 connected to two paperguides 301a and 301b, respectively, are synchronized by rotation members303, 313, 321, and 322. Where a construction is adopted in which thepaper guides 301a and 301b are supported by a parallel link so that theycan swing in parallel, other than a mechanism for synchronizing therocking members on the two sides by gears etc., a symmetrical movementmechanism using a pantograph link etc. can be adopted.

The relative movement of the locking releasing pieces 306a and 306b onthe two sides connected by the symmetrical movement mechanism 314 withrespect to the paper guide thereof is transferred to the secondsymmetrical movement mechanism 314 even in a case where one of them isoperated. The second symmetrical movement mechanism 314 performs thesame motion when any of the locking releasing pieces 306a and 306b isoperated. Accordingly, if the locking mechanism 317 is connected to thissecond symmetrical movement mechanism 314 and the locking is released,even if one of the locking releasing pieces is operated, the locking ofthe paper guides 301a and 301b is released.

Also, when the paper guides 301a and 301b are moved, the secondsymmetrical movement mechanism 314 performs the same motion as that ofthe symmetrical movement mechanism 304 connecting the paper guides 301aand 301b and absorbs the change of interval between the lockingreleasing pieces 306a and 306b at the two sides. Accordingly, the secondsymmetrical movement mechanism 314 performs two functions, i.e., afunction of transferring the locking releasing force and a function ofenabling a symmetrical movement of the locking releasing pieces 306a and306b on the two sides.

Also, the same types are used in parallel as the (first) symmetricalmovement mechanism 304 and the second symmetrical movement mechanism314, and therefore the shaft supporting construction of the guides offor example the linear movement members 302 (302a, 302b), 312 (312a,312b), 323, and 324, and the rotation members 303, 313, 321 (321a,321b), and 322 (322a, 322b) can be made common, and the increase of costdue to the provision of the second symmetrical movement mechanism 314can be minimized.

A detailed explanation will be made below of the embodiment shown inFIG. 19 to FIG. 26.

FIG. 19 to FIG. 24 show a first embodiment of the guide mechanism havinga variable width. To the paper guides 301a and 301b attached to thehopper (paper holder) 3 (FIG. 1) so that linear movement can be freelyperformed in the width direction of the paper, as shown in FIG. 26,racks 302a and 302b similar to those in the conventional apparatus aresecured. These racks 302a and 302b are engaged with the two sides of thepinion 303 secured in the free rotation state to the center of the paperstand, whereby the symmetrical movement mechanism 304 is constituted.

On the back surface of the paper guides 301a and 301b, the lockingreleasing pieces 306a and 306b are pivotally supported by the pins 305aand 305b in a direction parallel to the side of the paper. At least onelocking releasing piece 306a is biased by the spring 307 toward theoutside. The tongue pieces 308a and 308b extended downward areintegrally provided in the locking releasing pieces 306a and 306b. Thesetongue pieces 308a and 308b are freely fitted in square holes 309a and309b provided in the second racks 312a and 312b attached in the stackedstate on the aforesaid racks 302a and 302b in a slightly rockable state.The two second racks 312a and 312b are engaged with the two sides of thesecond pinion 313 which has the same shaft as the aforesaid pinion 303and independently axially supported in the free rotation state.

When the right side locking releasing piece 306a is gripped in a spacewith the guide wall of the paper guide 301a and the locking releasingpiece 306a is pivoted inward, due to the rocking of the tongue piece308a to the outside, the second rack 312a on the right side is moved tothe outside. This movement motion is transferred via the second pinion313 to the second rack 312b on the left side to move this to the outsideand swing the tongue piece 308b of the locking releasing piece 306b onthe left side connected to the left side second rack 312b by theconnection pin 309b to the left side. Therefore, also the lockingreleasing piece 306b on the left side swings to the inside. Also, whenthe locking releasing piece 306b on the left side is operated,similarly, the locking releasing piece 306a on the right side swings tothe inside.

Also, even in a state where the locking releasing pieces 306a and 306bare rocked inward, the second symmetrical movement mechanism 314 is notimpaired in its original function, and therefore if one of the paperguides 301a and 301b is operated in this state, the paper guides 301aand 301b on the two sides symmetrically move by the function of thesymmetrical movement mechanism 304, and the locking releasing pieces306a and 306b on the two sides symmetrically move together with thepaper guides 301a and 301b by the function of the second symmetricalmovement mechanism 314. Even during this movement, due to the rocking ofthe locking releasing piece 306a, a state where the second racks 312aand 312b move to the outside is maintained, and therefore also a statewhere the locking releasing pieces 306a and 306b on the two sides aresynchronously rocked is maintained.

The locking shaft 315 is fixed on the paper stand parallel to thedirection of movement of the paper guide 301a. The through-hole (lockinghole) 316 provided in the tongue piece 308a of the locking releasingpiece on the right side of the figure is loosely fitted on this lockingshaft 315. The tongue piece 308a of the locking releasing piece 306a isprovided in a direction orthogonal to the locking shaft 315 when thelocking releasing piece 306a is slightly pivoted inward. When thelocking releasing piece 306a is pivoted to the outside by the spring307, the tongue piece 308a of the locking releasing piece becomesoblique relative to the locking shaft 315, so that upper and lowerpieces of the locking shaft 315 and the through-hole 316 abut againsteach other, whereby the rocking angle of the locking releasing pieces306a and 306b to the outside is regulated (a part of enlarged view ofFIG. 21).

When the paper guides 301a and 301b are pushed to move to the outside ina state where the locking releasing piece 306a is pivoted to the outsidein this way, the tongue piece 308a of the locking releasing piece 306ais further inclined with respect to the locking shaft 315, and thereforethe upper and lower pieces of the locking shaft 315 and the through-hole316 are strongly pressed, to inhibit movement of the paper guides 301aand 301b. Namely, in this embodiment, the locking mechanism 317 isconstituted by the locking shaft 315 and the through-hole 316 providedin the tongue piece 308a of the locking releasing piece on the rightside of the figure. The locking is performed by the biasing force of thespring 307, and the movement of the paper guides 301a and 301b isinhibited. In a locking mechanism having such a construction, theresistance with respect to the force moving the paper guides 301a and301b to the inside is weak, but the movement of the paper guides to theinside is inhibited by the side of the paper guided by this, andtherefore there arises no problem. This rather smoothens the movement ofthe paper guides 301a and 301b to the inside.

The above-described embodiment uses the rack and pinion mechanism as thesymmetrical movement mechanism. As shown in FIG. 24, wires 323 and 324are suspended around pulleys 321a and 321b and 322a and 322b having thesame shape, which are axially supported at the two sides in a stateenabling them to freely rotate, so that the paper guides 301a and 301bare brought into association with one wire 323. The locking releasingpieces 306a and 306b are brought into association with the other wire324, whereby the symmetrical movement mechanism 304 for the paper guideand the second symmetrical movement mechanism 314 for the lockingreleasing piece can be constituted. In this case, the paper guides 301aand 301b and locking releasing pieces 306a and 306b on the two sides ofcourse must be connected to the opposite positions sandwiching thepulleys of the wires 323 and 324, respectively.

FIG. 25 and FIG. 26 show another example of the locking mechanism whichcan be used in the apparatus of this invention, in which the rotation ofthe rotation members such as the pinions 303 and 313, the pulleys 321aand 322a, etc. interposed in the symmetrical movement mechanisms 304 and314 is locked. Explaining this by taking as an example a case ofmounting inside the pinions 303 and 313 of the embodiments of FIGS. 19to 23, a spring clutch 327 provided with a coil portion 326 elasticallysecured to the circumferential surface of the supporting shaft 325 inthe free state is inserted into the immoveable supporting shaft 325supporting the pinions 303 and 313 at the shaft in the free rotationstate. The two ends of this spring clutch are engaged with the firstpinion 303 and the second pinion 313, respectively. The windingdirection of the spring clutch 327 around the supporting shaft 325 is adirection in which the spring clutch 327 is wound again by the relativepivoting of the second pinion 313 with respect to the first pinion 303when the second racks 312a and 312b move to the outside with respect tothe first racks 302a and 302b, and the coil portion 326 is loosened.

This spring clutch 327 performs a function of inhibiting the motion ofthe first and second pinions 303 and 313, that is, the first and secondsymmetrical movement mechanisms 304 and 314, when the coil portion 326comes into close contact with the support shaft 325 in the free stateand, at the same time, performs another function in which the secondracks 312a and 312b are biased toward the inside with respect to thefirst racks 302a and 302b, to keep the locking releasing pieces 306a and306b in the opened state. It performs the same function as that of thespring 307 shown in FIG. 21.

In this construction, when either one of the locking releasing pieces306a and 306b is operated, the second racks 312a and 312b connected tothis move relatively to the outside with respect to the first racks 302aand 302b. By the relative pivoting of the second pinion 313 with respectto the first pinion 303 produced by this, the fixed state with respectto the support shaft 325 of the spring clutch 327 is released. The firstpinion 303 and the second pinion 313 are made integral around thesupport shaft 325 in a state retaining the mutual relative phase angleto become freely rotable in state.

Accordingly, when either one of the locking releasing pieces 306a and306b is operated to operate the paper guides 301a and 301b, after thelocking by the spring clutch 327 is released, the first pinion 303 andthe second pinion 313 are integrally rotated, whereby it becomespossible to move the paper guides 301a and 301b to the free positionretaining their symmetrical positional relationship. By releasing theoperating force of the locking releasing pieces 306a and 306b, therotation of the pinions 303 and 313 is locked, to inhibit the movementof the paper guides 301a and 301b.

According to this embodiment explained above, it becomes possible tomove the paper guides on the two sides to any position while retainingthe symmetrical relationship thereof by releasing the locking byoperating either one of locking releasing pieces provided in the twopaper guides, positioned symmetrically with the center reference.Therefore, it becomes possible to set up the paper guides by one handfrom any side of the apparatus, and there is an effect of an improvementof the operability. Also, since the paper guides are kept by the lockingmechanism in the set position, the paper guides will not be opened byvibration etc. during use, and also the motion of the paper guide at thesetting of the position is smooth.

FIGS. 27 to 29 show an embodiment applying the present invention to acomposite type image reading apparatus in which the optical reading unitis fixed, and both of the automatic paper feeding and reading forreading the document by movement and the flat bed reading for performingreading by fixing the document and moving the optical reading unit arepossible. A particular improvement is directed to the method of giving awhite reference in the image reading apparatus.

In general, in the image reading of the document, the white referencesheet attached to the apparatus is read by the optical reading unit,whereby the absolute white level with respect to the light source is setup. In the automatic paper feeding and reading, the reading of thedocument is carried out by fixing the optical reading unit, but in theconventional document reading apparatus, the white reference was placedon the flat bed reading portion side, and therefore it was necessary toperform the reading of the white reference by moving the optical readingunit.

The optical reading unit moves beneath the white reference sheet beforethe start of the reading of the documents and reads the white reference,thereafter returns to the reading position (first reading position) ofthe automatic paper feeding and continuously reads the image on thesurface of the document passing above.

Also, at the flat bed reading, the document is placed on the flat bed,the optical reading unit first reads the white reference beneath thewhite reference sheet, and thereafter proceeds beneath the flat bed(second reading position) and reads the document on the flat bed whilemoving.

Therefore, in the embodiment shown in FIGS. 27 to 29, in the compositetype image reading apparatus of automatic paper feeding and reading andflat bed reading, to shorten the time required for the white referencereading at the automatic paper feeding and reading and to improve thethrough-put, a white reference is provided on the side opposite to theoptical reading unit. Before the document is fed to the readingposition, the reading of white reference is made possible by the opticalreading unit.

FIG. 27 is a structural diagram of the principle thereof and shows onlya principal part of the image reading apparatus of the two-side documentreading type. Parts corresponding to those in the above-mentionedembodiments are shown by the same numerals and an overlappingexplanation will be omitted.

"a₁ " and "a₂ " are reading positions for reading the front surface andback surface of the document, respectively.

Reference numerals 101a and 101b are platen glasses for reading thefront surface and back surface of the document.

Reference numerals 416a and 416b are white reference sheets for readingthe front surface and back surface of the document and are adhered tothe platen glasses 101a and 101b.

The document is fed between the platen glasses 101a and 101b by the feedrollers 9 and ejected by the eject rollers 13. This document feedingpassage 23 is indicated by an arrow.

Where the document is not fed, the optical reading unit 21 can read thewhite reference sheet 416b adhered to the platen glass 101b through theopposite platen glass 101a at the reading position "a₁ ", and similarlythe optical reading unit for the back surface reading, the illustrationof which is omitted, can read the white reference sheet 416a adhered tothe platen glass 101a at the reading position "a₂ ".

Next, when the document is fed to the reading positions "a₁ " and "a² ",the white reference sheet is hiddened in back of the document. Forexample, the optical reading unit 21 operates so as to read the frontsurface of the passing document.

In FIG. 27, during the automatic paper feeding and reading, the opticalreading unit 21 can sequentially read the white reference sheet 416b andfront surface of the document while being fixed at the illustratedposition. During flat bed reading, after reading the white referencesheet 416b at the illustrated position, the optical reading unit 21moves beneath a flat bed 700 (FIG. 28) on the right, the illustration ofwhich is omitted, and performs the reading of the document on the flatbed. Note that, the flat bed is used when reading a document whichcannot be stacked on the hopper 3, for example, a book.

In the conventional example, the white reference sheet was arranged at aposition separate from the automatic paper feeding and reading position,but in the invention of the present application, it is provided at theautomatic paper feeding and reading position, and therefore a largemovement of the optical reading unit for reading the white reference isnot required. Therefore, the time for the reading operation of thedocument can be shortened.

FIG. 28 shows the structure of a concrete embodiment of FIG. 27. In FIG.28, 418 is a reading position of the back surface of the document; 419aand 419b are thin plate glasses for the cover; 421a and 421b aretwo-surface adhesion tapes; 25a and 25b are lamps for illuminating thedocument; 27 is a mirror; 31 is a lens; 33 is a CCD; 428 is a platespring; and 429 is a projection.

The white reference sheets 416a and 416b are held between the platenglasses 101a and 101b and the thin plate glasses 419a and 419brespectively in a sandwiched state and retained, and the platen glassesand the thin plate glasses are adhered by the two-surface adhesion tapes421a and 421b, respectively. Where there is no document at the readingposition, the white reference sheets 416a and 416b are illuminated bythe lamps 25a and 25b, respectively, and the reflection light is read bythe CCD 33 inside the optical reading unit 21.

The platen glass 101a is constituted so that it can move slightlyleftward (about 2 to 3 mm) and is usually pressed rightward by the platespring 428. At the reading of the front surface of the document, theoptical reading unit 21 is moved slightly (2 to 3 mm) rightward from theillustrated position. During this movement, the white reference sheet416b is read by a plurality of rasters. The signal is sent to a whitelevel follower circuit (usually provided in the image readingapparatus). The disturbance of the white reference level due to dust orstain deposited on the platen glass is removed to set the whitereference.

At the reading of the back surface of the document, the optical readingunit 21 is moved leftward and the platen glass 101a is moved leftward(by 2 to 3 mm) against the force of the plate spring 428 by theprojection 429. During this movement, the white reference sheet 416a isread by a plurality of rasters by the CCD for reading the back surface(the illustration is omitted). In the same way as that mentioned before,the influence of dust or stains on the white reference level iseliminated to set up the white reference.

A detailed explanation of the processing for setting the white reference(controller) will be made by FIG. 29.

Step S1: Control for moving the optical reading unit from the initialposition of FIG. 28 is started. In the case of the front surfacereading, it is moved rightward, while in the case of the back surfacereading, it is moved leftward. The number of rasters of the whitereference read during the movement is made b. Also, the variable n isdefined as: 1≦n≦b.

S2: The CCD output V_(m0) at the point of time of starting the movementis read for each bit position X_(m) and is recorded.

S3: Movement of one raster is performed (n<n+1). The CCD output V_(mn)at that time is read.

S4: The previous CCD output V_(m)(n-1) and the present CCD output V_(mn)are compared at each bit position X_(m). When the former is larger, stepS5 is executed, while when the latter is larger, step S6 is executed.

S5: When the previous value is larger than the present value, thepresent value is corrected to the previous value (V_(mn) =V_(m)(n-1)).

S6: When the present value is larger than the previous value, theprevious value is increased exactly by a value obtained by multiplyingthe difference between the previous value and the present value (V_(mn)-V_(m)(n-1) ) by a constant a (0<a<1).

V_(mn) =V_(m)(n-1) X {1+(V_(mn) - V_(m)(n-1)) X a}

S7: The processing from S3 to S7 is repeated until n becomes equal tothe defined raster number b, and the operation proceeds to step S8 whenn becomes equal to b.

S8: The optical reading unit is restored to the initial position shownin FIG. 28.

S9: The feeding of document is started and the image is read.

In the processing of steps of S4, S5, and S6 mentioned above, at thewhite reference reading of the continuous rasters, when the presentvalue is smaller than the previous value, the present value is abandonedand the previous value is held, while when the present value is largerthan the previous value, the white level is corrected to the larger oneby the method of performing a correction only with a constant proportionof the increased amount.

Accordingly, as exemplified by [1], [2], and [3] at the right bottom ofFIG. 29, even if the CCD output due to the dust is reduced in the rasterof [1] and the disturbance of the white level occurs, if the normalwhite reference reading is carried out by the subsequent raster, it ispossible to gradually obtain a proper white level as in [2] and [3].

The embodiment explained above is for two-side reading, and thereforewhite reference sheets were adhered to the front surface and backsurface platen glasses, respectively, but in the case of a one-sidereading apparatus etc., it is also possible to adhere the whitereference sheet to an appropriate member such as a back abutment memberin the vicinity of the reading position or the like.

According to this embodiment, it is not necessary to excessivelyincrease the dimensions of the apparatus for the attachment of the whitereference sheets, and an increase of the through-put can be achievedwithout the problem of degrading the attachment strength of the frameplate. Further, it becomes possible to effectively cope with thedisturbance of the white reference due to stains of the white referencesheet surface, and therefore the quality of the reading image can beimproved.

FIG. 30 is an explanatory view of the structure diagrammatically showinga modified embodiment of FIG. 1. The same parts are indicated by thesame reference numerals as those in the aforesaid FIG. 1. In FIG. 30,521 is a pick arm, which is provided on the shaft of the gear 18 so thatit can swing and, at the same time, a pick roller 5a and a gear 522 areprovided on the rocking end so that they can rotate. Note that, the gear522 is engaged with the gear 18. Reference numeral 523 is a spring,provided between the rocking end of the pick arm 521 and the main bodyof the apparatus with tension, which is formed so as to bias the pickarm 421 in the clockwise direction. Next, 524 is a gear, which isprovided so that it can pivot in engagement with the aforesaid gear 18.At the same time, an actuation arm 525 is coaxially provided and formedso that the pivoting end of this actuation arm 525 becomes able to beengaged with or disengaged from the aforesaid pick arm 521. Note that, atorque limiter (not illustrated) is attached to the shaft of the gear524 and formed so as to limit the torque where the actuation arm 525pivots in the counterclockwise direction and makes the pick arm 521pivot in the counterclockwise direction to the predetermined value orless. Reference numeral 526 is a sensor, which is provided in thedocument conveyance passage between the pick roller 5a and theseparation roller 5b in the vicinity of, for example, the gate 57. Therest of the structure is similar to that shown in FIG. 1 or FIG. 52.

An explanation will be made next of the function of the above-describedstructure. First, in FIG. 30, when the pulley 506 is rotated by thedrive motor 51 in a direction indicated by a broken arrow, the feedroller 9a rotates in the counterclockwise direction by a belt 507 andprepares for the front edge alignment in a case where the documentarrives. Simultaneously, also the pick roller 5a and the separationroller 5b rotate in the same direction, and therefore one sheet amongthe documents 1 (FIG. 1) stacked on the document stand 3 is fetched bythe pick roller 5a, passes the separation roller 5b, and is conveyed tothe feed roller 9a, where the above-mentioned front edge alignment iscarried out.

The document front edge alignment time by the above-described feedroller 9 is controlled by the preliminarily set pulse number or timeafter the passing of the document is detected by a sensor 526, which isthe same as the embodiment of FIG. 1 described before. In this case, forexample, when the document is thick and cannot be fetched even by therotation of the pick roller 5a, that is, when the document does notreach the sensor 526, the gear 524 pivots in the direction indicated bya broken arrow via the gear 18. Then, also the actuation arm 525provided coaxially with the gear 18 pivots in the same direction,engages with the rocking end of the pick arm 521, and pivots the pickarm 521 in the counterclockwise direction against the tension of thespring 523. By the pivoting of this pick arm 521, the pick roller 5a ispressed upward with the preliminarily set torque as a limit, andtherefore the pressing force against the document is increased and thedocument can be reliably fetched.

Next, after the completion of the fetching of the document, when thefront edge alignment processing by the feed roller 9 is ended, the feedroller 9 rotates in the direction indicated by a solid arrow, so thatthe conveyance of the document is carried out. On the other hand, by therotation of the feed roller 9 in the direction indicated by the solidarrow, the gear (not illustrated) provided coaxially with the pickroller 5a and separation roller 5b rotates in the reverse direction tothat in FIG. 30, but the one-directional clutch is attached to theserollers as mentioned before, and therefore it does not rotate andremains in the stopped state. Then, by the rotation of the gear 18 inthe counterclockwise direction, the gear 524 pivots in the directionindicated by the solid arrow, and therefore the actuation arm 525 isdetached from the pick arm 521 and returns to its original positionshown in for example FIG. 30.

During the rotation of the above-described pulley 50, feed rollers 9,and eject rollers 13 in the direction indicated by the solid arrow, bothof the pick roller 5a and the separation roller 5b are in the stoppedstate. Namely, the one-directional clutch is attached to the pick roller5a and the separation roller 5b, and therefore even if the gear 53rotates in the direction indicated by the solid arrow, this rotation isnot transferred to the pick roller 5a and the separation roller 5b.Accordingly, the subsequent document is not directly conveyed to thefeed rollers 9 rotating in the direction indicated by the solid arrow.

After the rear end of the preceding document is detected by the sensor105, the drive motor 51 rotates in reverse after an elapse of thepreliminarily set pulse numbers or time and the pulley 50 and the feedroller 9 rotate in the direction indicated by a broken arrow, tocomplete the preparation for the front edge alignment of the nextdocument. Simultaneously, also the pick roller 5a and the separationroller 5b rotate in the direction indicated by the broken arrow, and thenext document is fetched. During this time, even if the precedingdocument remains in an engagement state with the eject rollers 13, theeject rollers 13 are in the stopped state, therefore the inconvenienceof the preceding document being conveyed in the reverse direction doesnot occur.

FIG. 31 is an explanatory view of the structure further diagrammaticallyshowing a modified embodiment of FIG. 30, wherein the same parts areindicated by the same reference numerals as those in the aforesaid FIG.30. In FIG. 31, the hopper 3 is formed so that it can swing about thevicinity of the pick roller 5a and can swing from the position indicatedby the solid line to the position 3' indicated by for example a chainline. Reference numeral 531 is a rocking arm, provided beneath thehopper 3 so that it can swing and is formed so that the left end portioncan be engaged with and disengaged from the actuation arm of 533mentioned later and the right end portion can be engaged with anddisengaged from the bottom portion of the hopper 3, respectively. Next,532 is a gear, which gear 522 is provided so that it can pivot inengagement. At the same time, the actuation arm 533 is coaxiallyprovided. The pivoting end of this actuation arm 533 can be engaged withor disengaged from the left end portion of the aforesaid rocking arm531. Note that, a torque limiter (not illustrated) is attached to theshaft of the gear 532, and the actuation arm 533 pivots in the clockwisedirection, to restrict the torque when the rocking arm 531 is pivoted inthe counterclockwise direction by a predetermined value or less. Therest of the structure is similar to that of FIG. 30.

In the above-described structure, the document front edge alignmentfunction and the processing function thereafter are similar to those inthe embodiment of FIG. 1 and the embodiment of FIG. 30 described before.Therefore, explanations of these are omitted. An explanation will bemade of the fetching function of the document. First, for example, whena document is not fetched even by the rotation of the pick roller 5a,that is, when no document reaches the sensor 526, the gear 532 pivots inthe direction indicated by the broken arrow via the gear 522. Then, alsothe actuation arm 533 provided coaxially with the gear 532 pivots in thesame direction, engages with the left end portion of the rocking arm531, makes the rocking arm 531 pivot in the counterclockwise direction,and swings the same to the position indicated by the chain line. Sincethe document stand 3 swings to the position 3' indicated by the chainline by the above-described rocking of the rocking arm 531, theinclination angle of the document with respect to the horizontal planeis increased, and the sliding function of the document into the pickroller 5a is assisted, so that the state of 32B is formed and thus thefetching of the document becomes smooth. Note that, FIG. 32A shows astate where the front edge alignment of the paper 1 is not carried out,and 32B indicates a state where the front edge alignment is carried out.Particularly, in the case of a bottom take-out type paper feedingsystem, when a large number of sheets of document 1 as shown in FIG. 32Bis set on the hopper 3, so as to smoothly and reliably perform thefetching of the documents into the separation roller, as shown in FIG.32B, a pre-operation must be carried out so that the front end of thedocument 1 forms a knife edge.

Next, after the completion of the fetching of the documents, when thefront edge alignment processing by the feed roller 9 is ended, the feedroller 9 rotates in the direction indicated by the solid arrow, and theconveyance of the document is carried out. On the other hand, the gear532 pivots in the direction indicated by the solid arrow via a middlegear train with which the gear 532 is engaged, and therefore theactuation arm 533 is detached from the rocking arm 531 and returns toits original position as shown in for example FIG. 31. In this case, thepick roller 5a and the separation roller 5b do not rotate, but remain inthe stopped state, in the same way as in the aforesaid embodiment.

In the bottom take-out type automatic paper feeding mechanism asmentioned above, every time one sheet of the lowermost documents 1 istaken out of the hopper (shooter) 3, the document 1 slides and rubs onthe upper surface of the hopper, and therefore static electricity is aptto be generated. The generation of the static electricity isparticularly conspicuous in a low humidity environment. Therefore,frequently, the document 1 is adhered to the hopper 3 by the staticelectricity and a picking error of the document 1 is caused. Also, asthe hopper capacity becomes larger, picking error occurs morefrequently. So as to solve this, as shown in FIG. 33, preferablyprojections 600 are provided on the upper surface of the hopper 3 in adirection orthogonal to the conveyance direction of the document (FIG.40) or on both sides of the conveyance direction of the document. Theprojections 600 are appropriately distributed on the upper surface ofthe hopper 3 at appropriate intervals. The projections 600 preferablyexhibit a semi-spherical shape to reduce the contact surface area withthe paper 1 to as small as possible. Thus, there is exhibited a statewhere several portions of the paper 1 float with respect to the uppersurface of the hopper 3 by the projections 600, not a state of closecontact of the entire surface, and the problem of the picking errorsaccompanying the static electricity is greatly reduced.

It is also possible to form the projections 600 on the guides 301 (301aand 301b) explained referring to FIG. 19, as shown in FIG. 34.

Alternatively, in place of the provision of the projections 600, it isalso possible to adhere a material having a quality close to that of thedocument 1 from the viewpoint of the train of the electric charges, thatis a member (for example sheet) having a quality is resistant to thegeneration of static electricity between the same and the document 1 tothe upper surface of the hopper 3 or the upper surface of the guides 301(301a, 301b) as shown in FIG. 35. Alternatively, it is also possible toform the hopper 3 and the guides 301 per se by such a material. Thematerial is appropriately selected by the material of the document 1.Where the document 1 is paper, an aluminum-coated sheet, a sheet made ofcork, etc. are adaptable as ones having a close electric charge train.

Finally, an explanation will be made of various types of correction(magnification correction in the sub-scanning direction and offsetcorrection) executed in the present invention for improvement of thequality of the read image.

First, an explanation will be made of the magnification correction inthe sub-scanning direction.

Initial correction

A reference medium (document) 1A as shown in FIG. 36 is prepared. Thecorrect dimension S (unit: mm) of the reference medium 1A betweenreference points O has been preliminarily measured. This referencemedium 1A is applied to the image reading apparatus of the presentinvention to detect the number of pulses P corresponding to the distanceS. The unit amount of paper feed v per pulse is learned, then the amountof deviation peculiar to the related image reading apparatus (due to thevariation of diameter of various types of rollers and inter-rollerdistance etc.) is detected from the following equation:

    u=A/v

wherein, u is the number of pulses in a calculation necessary for movingthe distance S.

Accordingly, when it is assumed that the set speed (design value) of themotor (for example, stepping motor) 51 is M1, the motor speed M2 whichshould be corrected is obtained by:

    M2=(P/u) x M1

By this, the initial correction of the motor 51 can be carried out.

Temperature correction

The change of the feed roller diameter by the ambient temperature andthe change of the feeding force/back load are corrected as follows:

Note that, the feeding force/back load means the balance between theforce in the direction of feeding the documents by the feed rollers andthe friction resistance by the separation pad 7.

The temperature sensor TS (FIG. 1) measuring the ambient temperature isprovided for example in the vicinity of the shafts of the feed rollers9. From the measurement value n₁ of the temperature sensor TS, accordingto the following equation, the speed correction value M3 of the steppingmotor 51 is found:

    M3=(1- Δm (n.sub.1 - n.sub.0)) x M1

wherein, Δm is the correction value per unit temperature: n₀ is thereference temperature (for example, ordinary temperature: 25° C.); andM1 is the set speed (design value) of the stepping motor 51.

In this way, if the temperature correction can be carried out, it is notnecessary to use an expensive metal roller in comparison with the priorart, which does not perform the temperature correction and accordinglymust use a feed roller made of metal having a small thermal expansioncoefficient.

Size correction

The feeding speed of paper having a long length L in the paper feedingdirection generally tends to be slower in comparison with paper having ashort length (FIG. 32). This is because, when the length L of the paperis long, the time from when the front end of the paper 1 passes theseparation pad 7 and the rear end thereof completely passes becomesrelatively long, and therefore the time of receiving the frictionalresistance by the separation pad 7 is prolonged by chat amount.

Therefore, desirably the length L of the paper is detected and the motorspeed is changed in accordance with this. It is also possible todirectly detect the length L of the paper, but there is a one-to-onecorrespondence of the lengths of the paper with standard sizes (A4, B4,B5, etc.), and therefore an existing size sensor is utilized as it is inthe present invention.

Namely, generally a paper size sensor is provided in the image readingapparatus as shown in FIG. 38. As this sensor, generally a contactswitch or an optical sensor is used. The switch or sensor is placed atthe portion indicated by the inverted triangle in FIG. 38. The papersize can be detected by the combination of ON and OFF signals thereof.

The motor speed is changed in accordance with the paper size detected inthis way. The relationship between the correction value of the motorspeed and the paper size may be preliminarily stored in the map of thememory of the controller.

FIG. 39 shows the situation of that control. It will be understood thatthe motor speed, that is, the sub-scanning magnification, is correctedin accordance with the paper size with respect to the referencesub-scanning magnification (0%).

Offset correction (main scanning direction)

There is a possibility that the reading position by the reading unitwill deviate in the main scanning direction (scanning direction of thebeam) due to the thermal expansion and shrinkage of the document cover.This deviation can also be corrected by the following equation inaccordance with the detection temperature n₁. ##EQU1## Note, M4 denotesthe offset correction value: Δα denotes the amount of expansion andshrinkage per unit temperature; and g denotes the basic resolution (dpi)of the related apparatus, respectively.

FIG. 40 shows the schematic outer appearance of the image readingapparatus according to the present invention for reference.

Finally, the basic concept concerning the improvement of the portionsmentioned above can be applied to both of the one-side reading andtwo-side reading.

CAPABILITY OF EXPLOITATION IN INDUSTRY

The present invention can be applied to all apparatuses readinginformation using an image reading apparatus such as a facsimile orimage scanner.

We claim:
 1. An image reading apparatus having a bottom take-out typeautomatic paper feeding apparatus which sequentially takes outsheet-like paper stacked on a hopper one by one from the lowermost sheetby separation by paper feed rollers arranged at the front edge sidethereof and a separation member coming into contact with said paper feedrollers,said paper feed rollers being constituted by a first rollerpositioned on the upstream side of a paper feeding direction and asecond roller positioned on the downstream side; the apparatus furtherhaving a fixed gate plate forming a slit having a predetermined widthallowing the passing of a predetermined number of sheets of papertherethrough in a space between the gate plate and the first rollerprovided at the first roller so as to face the first roller.
 2. An imagereading apparatus as set forth in claim 1, wherein said gate plate isinclined in a paper feeding direction.
 3. An image reading apparatus asset forth in claim 1, wherein said separation member is constituted by aseparation pad coming into surface-contact with the circumferentialsurface of the second roller.
 4. An image reading apparatus as set forthin claim 2, wherein the inclination angle of said gate plate isvariable.
 5. An image reading apparatus comprising a bottom take-outtype automatic paper feeding apparatus which sequentially takes outsheet-like paper stacked on a hopper one by one from the lowermost sheetby separation by paper feed rollers arranged at the front edge sidethereof and a separation member coming into contact with said paper feedrollers, said paper feed rollers being constituted by a first rollerpositioned on the upstream side of a paper feeding direction and asecond roller positioned on the downstream side; a gate plate variablyinclined in a paper feeding direction and forming a slit having apredetermined width allowing the passing of a predetermined number ofsheets of paper therethrough in a space between the gate plate and thefirst roller provided at the first roller so as to face the firstroller; an empty sensor which detects whether or not paper exists on thehopper; a first paper feeding detection sensor detecting the existenceor nonexistence of paper between said first roller and second roller;and a gate opening and closing motor moving the gate plate ininclination; wherein the inclination angle of the gate plate becomessmall when the empty sensor detects the absence of the paper and theinclination angle is increased when the first paper feeding detectionsensor does not detect paper after the empty sensor detects theexistence of the paper and a predetermined time elapses from thestarting of rotation of the first roller.
 6. An image reading apparatusas set forth in claim 1, wherein the first roller is provided in a pickarm formed so that it can swing and is formed so that the pressing forceagainst the document becomes variable; an actuation arm formed so thatit can pivot selectively in association with said first roller isprovided so that it can be engaged with or disengaged from said pickarm; and said pick arm is rocked by the selective pivoting of thisactuation arm, whereby the pressing force of the first roller againstthe document is increased.
 7. An image reading apparatus comprising abottom take-out type automatic paper feeding apparatus whichsequentially takes out sheet-like paper stacked on a hopper one by onefrom the lowermost sheet by separation by paper feed rollers arranged atthe front edge side thereof and a separation member coming into contactwith said paper feed rollers, said paper feed rollers being constitutedby a first roller positioned on the upstream side of a paper feedingdirection and a second roller positioned on the downstream side; a gateplate forming a slit having a predetermined width allowing the passingof a predetermined number of sheets of paper therethrough in a spacebetween the gate plate and the first roller provided at the first rollerso as to face the first roller; a document stand constituting the hopperformed so that it can swing about the vicinity of the first roller; anactuation arm formed so that it can pivot selectively in associationwith said first roller provided on said document stand directly or viaanother rocking arm so that it can be engaged therewith or disengagedtherefrom; wherein said document stand is rocked by the selectivepivoting of said actuation arm, whereby the inclination angle withrespect to the horizontal plane of the document is increased.